From 2f630e1ce18ad2e07428296532a68b11dc66ad10 Mon Sep 17 00:00:00 2001 From: Illia Volochii Date: Wed, 17 May 2023 11:49:20 +0300 Subject: gh-102153: Start stripping C0 control and space chars in `urlsplit` (#102508) `urllib.parse.urlsplit` has already been respecting the WHATWG spec a bit #25595. This adds more sanitizing to respect the "Remove any leading C0 control or space from input" [rule](https://url.spec.whatwg.org/#url-parsing:~:text=Remove%20any%20leading%20and%20trailing%20C0%20control%20or%20space%20from%20input.) in response to [CVE-2023-24329](https://nvd.nist.gov/vuln/detail/CVE-2023-24329). --------- Co-authored-by: Gregory P. Smith [Google] --- Doc/library/urllib.parse.rst | 46 +++++++++++++++- Lib/test/test_urlparse.py | 61 +++++++++++++++++++++- Lib/urllib/parse.py | 12 +++++ .../2023-03-07-20-59-17.gh-issue-102153.14CLSZ.rst | 3 ++ 4 files changed, 119 insertions(+), 3 deletions(-) create mode 100644 Misc/NEWS.d/next/Security/2023-03-07-20-59-17.gh-issue-102153.14CLSZ.rst diff --git a/Doc/library/urllib.parse.rst b/Doc/library/urllib.parse.rst index 96b3965..5a9a53f 100644 --- a/Doc/library/urllib.parse.rst +++ b/Doc/library/urllib.parse.rst @@ -159,6 +159,10 @@ or on combining URL components into a URL string. ParseResult(scheme='http', netloc='www.cwi.nl:80', path='/%7Eguido/Python.html', params='', query='', fragment='') + .. warning:: + + :func:`urlparse` does not perform validation. See :ref:`URL parsing + security ` for details. .. versionchanged:: 3.2 Added IPv6 URL parsing capabilities. @@ -324,8 +328,14 @@ or on combining URL components into a URL string. ``#``, ``@``, or ``:`` will raise a :exc:`ValueError`. If the URL is decomposed before parsing, no error will be raised. - Following the `WHATWG spec`_ that updates RFC 3986, ASCII newline - ``\n``, ``\r`` and tab ``\t`` characters are stripped from the URL. + Following some of the `WHATWG spec`_ that updates RFC 3986, leading C0 + control and space characters are stripped from the URL. ``\n``, + ``\r`` and tab ``\t`` characters are removed from the URL at any position. + + .. warning:: + + :func:`urlsplit` does not perform validation. See :ref:`URL parsing + security ` for details. .. versionchanged:: 3.6 Out-of-range port numbers now raise :exc:`ValueError`, instead of @@ -338,6 +348,9 @@ or on combining URL components into a URL string. .. versionchanged:: 3.10 ASCII newline and tab characters are stripped from the URL. + .. versionchanged:: 3.12 + Leading WHATWG C0 control and space characters are stripped from the URL. + .. _WHATWG spec: https://url.spec.whatwg.org/#concept-basic-url-parser .. function:: urlunsplit(parts) @@ -414,6 +427,35 @@ or on combining URL components into a URL string. or ``scheme://host/path``). If *url* is not a wrapped URL, it is returned without changes. +.. _url-parsing-security: + +URL parsing security +-------------------- + +The :func:`urlsplit` and :func:`urlparse` APIs do not perform **validation** of +inputs. They may not raise errors on inputs that other applications consider +invalid. They may also succeed on some inputs that might not be considered +URLs elsewhere. Their purpose is for practical functionality rather than +purity. + +Instead of raising an exception on unusual input, they may instead return some +component parts as empty strings. Or components may contain more than perhaps +they should. + +We recommend that users of these APIs where the values may be used anywhere +with security implications code defensively. Do some verification within your +code before trusting a returned component part. Does that ``scheme`` make +sense? Is that a sensible ``path``? Is there anything strange about that +``hostname``? etc. + +What constitutes a URL is not universally well defined. Different applications +have different needs and desired constraints. For instance the living `WHATWG +spec`_ describes what user facing web clients such as a web browser require. +While :rfc:`3986` is more general. These functions incorporate some aspects of +both, but cannot be claimed compliant with either. The APIs and existing user +code with expectations on specific behaviors predate both standards leading us +to be very cautious about making API behavior changes. + .. _parsing-ascii-encoded-bytes: Parsing ASCII Encoded Bytes diff --git a/Lib/test/test_urlparse.py b/Lib/test/test_urlparse.py index e324bab..625c6dc 100644 --- a/Lib/test/test_urlparse.py +++ b/Lib/test/test_urlparse.py @@ -654,6 +654,65 @@ class UrlParseTestCase(unittest.TestCase): self.assertEqual(p.scheme, "http") self.assertEqual(p.geturl(), "http://www.python.org/javascript:alert('msg')/?query=something#fragment") + def test_urlsplit_strip_url(self): + noise = bytes(range(0, 0x20 + 1)) + base_url = "http://User:Pass@www.python.org:080/doc/?query=yes#frag" + + url = noise.decode("utf-8") + base_url + p = urllib.parse.urlsplit(url) + self.assertEqual(p.scheme, "http") + self.assertEqual(p.netloc, "User:Pass@www.python.org:080") + self.assertEqual(p.path, "/doc/") + self.assertEqual(p.query, "query=yes") + self.assertEqual(p.fragment, "frag") + self.assertEqual(p.username, "User") + self.assertEqual(p.password, "Pass") + self.assertEqual(p.hostname, "www.python.org") + self.assertEqual(p.port, 80) + self.assertEqual(p.geturl(), base_url) + + url = noise + base_url.encode("utf-8") + p = urllib.parse.urlsplit(url) + self.assertEqual(p.scheme, b"http") + self.assertEqual(p.netloc, b"User:Pass@www.python.org:080") + self.assertEqual(p.path, b"/doc/") + self.assertEqual(p.query, b"query=yes") + self.assertEqual(p.fragment, b"frag") + self.assertEqual(p.username, b"User") + self.assertEqual(p.password, b"Pass") + self.assertEqual(p.hostname, b"www.python.org") + self.assertEqual(p.port, 80) + self.assertEqual(p.geturl(), base_url.encode("utf-8")) + + # Test that trailing space is preserved as some applications rely on + # this within query strings. + query_spaces_url = "https://www.python.org:88/doc/?query= " + p = urllib.parse.urlsplit(noise.decode("utf-8") + query_spaces_url) + self.assertEqual(p.scheme, "https") + self.assertEqual(p.netloc, "www.python.org:88") + self.assertEqual(p.path, "/doc/") + self.assertEqual(p.query, "query= ") + self.assertEqual(p.port, 88) + self.assertEqual(p.geturl(), query_spaces_url) + + p = urllib.parse.urlsplit("www.pypi.org ") + # That "hostname" gets considered a "path" due to the + # trailing space and our existing logic... YUCK... + # and re-assembles via geturl aka unurlsplit into the original. + # django.core.validators.URLValidator (at least through v3.2) relies on + # this, for better or worse, to catch it in a ValidationError via its + # regular expressions. + # Here we test the basic round trip concept of such a trailing space. + self.assertEqual(urllib.parse.urlunsplit(p), "www.pypi.org ") + + # with scheme as cache-key + url = "//www.python.org/" + scheme = noise.decode("utf-8") + "https" + noise.decode("utf-8") + for _ in range(2): + p = urllib.parse.urlsplit(url, scheme=scheme) + self.assertEqual(p.scheme, "https") + self.assertEqual(p.geturl(), "https://www.python.org/") + def test_attributes_bad_port(self): """Check handling of invalid ports.""" for bytes in (False, True): @@ -661,7 +720,7 @@ class UrlParseTestCase(unittest.TestCase): for port in ("foo", "1.5", "-1", "0x10", "-0", "1_1", " 1", "1 ", "рем"): with self.subTest(bytes=bytes, parse=parse, port=port): netloc = "www.example.net:" + port - url = "http://" + netloc + url = "http://" + netloc + "/" if bytes: if netloc.isascii() and port.isascii(): netloc = netloc.encode("ascii") diff --git a/Lib/urllib/parse.py b/Lib/urllib/parse.py index da00739..b73b344 100644 --- a/Lib/urllib/parse.py +++ b/Lib/urllib/parse.py @@ -25,6 +25,10 @@ currently not entirely compliant with this RFC due to defacto scenarios for parsing, and for backward compatibility purposes, some parsing quirks from older RFCs are retained. The testcases in test_urlparse.py provides a good indicator of parsing behavior. + +The WHATWG URL Parser spec should also be considered. We are not compliant with +it either due to existing user code API behavior expectations (Hyrum's Law). +It serves as a useful guide when making changes. """ from collections import namedtuple @@ -80,6 +84,10 @@ scheme_chars = ('abcdefghijklmnopqrstuvwxyz' '0123456789' '+-.') +# Leading and trailing C0 control and space to be stripped per WHATWG spec. +# == "".join([chr(i) for i in range(0, 0x20 + 1)]) +_WHATWG_C0_CONTROL_OR_SPACE = '\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f ' + # Unsafe bytes to be removed per WHATWG spec _UNSAFE_URL_BYTES_TO_REMOVE = ['\t', '\r', '\n'] @@ -464,6 +472,10 @@ def urlsplit(url, scheme='', allow_fragments=True): """ url, scheme, _coerce_result = _coerce_args(url, scheme) + # Only lstrip url as some applications rely on preserving trailing space. + # (https://url.spec.whatwg.org/#concept-basic-url-parser would strip both) + url = url.lstrip(_WHATWG_C0_CONTROL_OR_SPACE) + scheme = scheme.strip(_WHATWG_C0_CONTROL_OR_SPACE) for b in _UNSAFE_URL_BYTES_TO_REMOVE: url = url.replace(b, "") diff --git a/Misc/NEWS.d/next/Security/2023-03-07-20-59-17.gh-issue-102153.14CLSZ.rst b/Misc/NEWS.d/next/Security/2023-03-07-20-59-17.gh-issue-102153.14CLSZ.rst new file mode 100644 index 0000000..e57ac4e --- /dev/null +++ b/Misc/NEWS.d/next/Security/2023-03-07-20-59-17.gh-issue-102153.14CLSZ.rst @@ -0,0 +1,3 @@ +:func:`urllib.parse.urlsplit` now strips leading C0 control and space +characters following the specification for URLs defined by WHATWG in +response to CVE-2023-24329. Patch by Illia Volochii. -- cgit v0.12